The present invention is in the field of thermostatic control and more specifically relates to a system which controls the temperature to a standby setting unless and until a command is applied to cause the system to control the temperature to a predetermined higher value.
It is well known that a thermostat may be used to control the operation of a furnace or heater to produce a nearly-constant temperature at the thermostat. In the type of system most commonly used in homes, the heat is supplied by a furnace and the thermostat is mounted on a wall in the room whose temperature is to be controlled. Typically, the furnace includes two electrical terminals. When a conductive path is established between these terminals, the furnace is turned on, but when the conductive path is opened, the furnace is turned off. A typical thermostat of the type used in homes includes a bimetallic element which is arranged to tilt a mercury switch so as to close the switch when the room temperature, also called the ambient temperature, falls below a preset temperature. The contacts of the thermostatic switch normally are connected to the terminals of the furnace, so that when the ambient temperature falls below the preset temperature, a conductive path is established between the two terminals of the furnace through the thermostat.
The typical thermostat control system described above normally includes means for setting in various selected temperatures which the system then seeks to maintain. With such a system, it is necessary to adjust the thermostat each time the ambient temperature is to be changed.
If it is known in advance that certain temperatures are desired at certain times of the day, the necessity for re-setting the thermostat can be avoided. It is known in the art to employ a clock-driven timer switch to cut in an override thermostat set to a higher temperature than the thermostat normally used. This permits the ambient temperature to be programmed between two temperature levels in a pattern which repeats from day to day.
Temperature programmed systems suffer from a lack of flexibility. Thus, where the pattern of temperature changes is too unpredictable to be forecast on a day-to-day basis, a system using a clock programmed switch is of little use.
In U.S. Pat. No. 3,159,212, issued Dec. 1, 1964 to Patrick, there is disclosed a portable thermostat which can be connected electrically to the furnace from one of a number of locations so as to be usable for controlling the temperature at a chosen location. While this offers some advantages with regard to heating efficiency, it does not eliminate the necessity of having to re-set the thermostat each time a temperature change is desired.
The present invention provides a greater degree of flexibility of operation than the systems of the prior art, and the present invention represents a definite improvement over the prior art systems in its ability to converse energy where the demand is irregular.